We are assessing the effects of amphetamine and tyramine injections on blood pressure, heart rate, and plasma catecholamines in healthy volunteers, and relationships among plasma catecholamines, circulatory variables, and physical exertion in patients with hemophilia. These studies take advantage of the assay techniques developed and validated in this laboratory for measuring plasma catecholamines. We also have re-analzed the raw data from another laboratory to assess possible age-dependence of hypertensive-normotensive differences in norepinephrine